1. Field of The Invention
The present invention relates to a voltage multiple dimming control apparatus, more particularly to, a voltage multiple dimming control apparatus for correctly generating pulse width modulation signals without using an analog to digital converter.
2. Description of The Prior Arts
Nowadays, LED plays a role of LCD backlight module, gradually, to replace the CCFL backlight module. And the dimming characteristics of the backlight module can provide a better viewing and power consumption saving. Compared with CCFL, LED can offer better dimming characteristics. Brightness for backlight, such as environmental light source sensing or color contents, for instance, can be manipulated in different approaches. Generally speaking, all of the various control approaches should be combined in order to reach an optimal value.
Refer to FIG. 1; a circuit diagram for conventional voltage multiple dimming control apparatus is illustrated, for which two dimming controls are included, and one of them is exhibited as pulse width modulation signal input terminal 1 whilst another is exhibited as a digital signal input 2. Furthermore, the conventional voltage multiple dimming control apparatus further comprises an additional input 3 so as to control the dimming frequency of a pulse width modulation generator.
The aforesaid pulse width modulation signal passes a low-pass filter thus its high-frequency ripples are filtered and its DC signal will be converted to a plurality of digital codes by an analog to digital converter 5.
The aforesaid digital codes should be digital in term of serial format or parallel format, which comprises a plurality of bits for signal dimming control. And the signal, overall speaking, will be used for further processing.
Also, two of the aforesaid dimming controls will be in process, and one of the processes is to multiplication of the two controls in order to obtain the desirable dimming rate. Unfortunately, a digital multiplier 6 will occupy a huge space and further consume a lot of power. Exemplarily, a multiplier characterized in 8 bits ×8 bits, requires at least 64 adders.
Accordingly, in view of the above drawbacks, it is an imperative that a voltage multiple dimming control apparatus is designed to generating a pulse width modulation signal without the cost of an analog to digital converter so as to solve the drawbacks as the foregoing and to further reduce the circuit die size and power consumption.